Method for metathesis of compounds comprising an olefinic double bond, in particular olefins

ABSTRACT

The invention relates to a method for metathesis of one or several reagents comprising a linear or branched hydrocarbon chain containing a double olefinic bond Csp 2 ═Csp 2  consisting in reacting said reagent or reagents with a supported metal compound comprising an aluminum oxide-based support to which a tungsten hydride is grafted. Typically, each said reagent or reagents comprises from 2 to 30 carbon atoms. The reagent can be embodied in the form of olefin. The inventive method can be used, for example for producing propylene from ethylene and butane.

The present invention relates to a process for the metathesis of one ormore reactants comprising an olefinic structure.

The reaction for the metathesis of olefins was discovered approximately40 years ago; it is a reversible transalkylidenation reaction, that isto say a reversible reaction for exchange of alkylidene groups within anolefin (self-metathesis) or a mixture of olefins (crossed metathesis);in some cases, these olefins can comprise functional groups. Equations(1) and (2) respectively represent the self-metathesis and crossedmetathesis reactions:

where R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈ represent hydrogen atoms orfunctionalized or nonfunctionalized hydrocarbon groups.

The first catalysts described by Philips Petroleum, who discovered thisreaction, were of heterogeneous type; they were composed essentially ofMoO₃ deposited on silica or alumina, operating at approximately 150-200°C. but unstable and deactivating, or of WO₃ deposited on the samesupports, operating at approximately 400-450° C.; the latter system,WO₃/SiO₂, remains the catalyst used industrially. The disadvantages ofthe latter system include the high temperatures, both for the reactionitself and for the regeneration of the catalyst.

It would be highly advantageous to have available a heterogeneouscatalytic system effective in the meta-thesis of reactants comprising anolefinic structure, e.g. olefins, which is capable of operating atrelatively low temperature and which can be regenerated at moderatetemperature.

An objective of the invention is thus to provide an effective processfor the metathesis of reactants comprising an olefinic structure, e.g.olefins, using a catalyst which is capable of operating at relativelylow temperature.

Another objective of the invention is to provide such a process in whichthe catalyst can be regenerated at moderate temperature.

A subject matter of the present invention is thus a process for themetathesis of one or more, preferably one or two, reactants comprising alinear or branched hydrocarbon chain comprising an olefinic double bondCsp²═Csp² (olefinic structure), in which this reactant or thesereactants is/are brought into the presence of a supported metal compoundcomprising a support based on aluminum oxide to which a tungsten hydrideis grafted.

The olefinic double bond is included in a linear or branched hydrocarbonchain of formula R₁R₂C═CR₃R₄ comprising an olefinic double bondCsp²═Csp² and identical or different substituents R_(i) (i=1 to 4) onthese carbons.

According to one characteristic of the invention, each reactantcomprises, in total, from 2 to 30 carbon atoms.

According to a first embodiment, the invention relates to the metathesisof one or more olefins or alkenes, namely unsaturated, linear orbranched, acyclic hydrocarbon(s), comprising a Csp²═Csp² double bondbetween two carbon atoms, of empirical formula C_(n)H_(2n) andpreferably with n an integer ranging from 2 to 30. The R_(i)substituents can, for example, be of the hydrogen, methyl, ethyl, propylor isopropyl, butyl, sec-butyl or isobutyl, or pentyl, sec-pentyl,isopentyl or neopentyl type.

According to a specific aspect of this embodiment, the invention relatesto a process for the production of propylene in which ethylene andbutene are reacted in the presence of the supported metal compoundcomprising a support based on aluminum oxide to which a tungsten hydrideis grafted.

According to a second embodiment, the reactant or reactants comprise(s)identical or different R_(i) substituents chosen from hydrogen atoms,saturated, linear or branched, hydrocarbon groups and saturated cyclichydrocarbon groups which optionally carry hydrocarbon substituents andwhich can be connected to the Csp² carbon of the olefinic double bondeither directly or via a saturated hydrocarbon chain. The cyclic R_(i)hydrocarbon substituents can, for example, be of the cyclopropyl,cyclobutyl, cyclopentyl or cyclohexyl type and the like or ofsubstituted cyclic type, such as methylcycloalkyl, ethylcycloalkyl,methylenecycloalkyl or of formula —(CH₂)_(n)-cycloalkyl. In addition tohydrogen, the other substituents optionally present can, for example, beof the methyl, ethyl, propyl or isopropyl, butyl, sec-butyl or isobutyl,or pentyl, sec-pentyl, isopentyl or neopentyl type.

According to a third embodiment, the reactant or reactants comprise(s)identical or different R_(i) substituents chosen from hydrogen atoms,saturated, linear or branched, hydrocarbon groups and aromatic ringswhich optionally carry saturated hydrocarbon substituents and which canbe connected to the Csp² carbon of the olefinic double bond eitherdirectly or via a saturated hydrocarbon chain. The R_(i) substituentscomprising aromatic rings can, for example, be of the phenyl, tolyl,benzyl, xylyl or biphenyl type or of formula —(CH₂)_(n)-aryl. Inaddition to hydrogen, the other substituents optionally present can, forexample, be of the methyl, ethyl, propyl or isopropyl, butyl, sec-butylor isobutyl, or pentyl, sec-pentyl, isopentyl or neopentyl type.

According to a fourth embodiment, different reactants chosen from thosedescribed in the preceding three series are reacted together.

The process of the invention can be carried out at a temperature rangingfrom 20 to 600° C. According to an advantageous characteristic of theinvention, the process is carried out at a relatively low temperatureranging from 20 to 350° C., preferably from 50 to 300° C., better stillfrom 80 to 200° C.

According to another characteristic, the process is carried out under anabsolute pressure ranging from 0.01 to 8 MPa, preferably from 0.01 to 1MPa, better still from 0.1 to 0.5 MPa.

The reactant or reactants can be made use of in the gaseous or liquidform.

The process can be carried out in the presence of hydrogen or of anagent which forms hydrogen in situ. Thus, the process can be carried outunder a hydrogen partial pressure ranging from 0.001 to 0.1 MPa. Mentionmay be made, as agent which forms hydrogen in situ, of cyclic compounds,such as cyclohexane, decahydro-naphthalene and tetrahydronaphthalene.

According to an advantageous characteristic of the invention, thecatalyst can be reactivated or regenerated by bringing into contact withhydrogen, in particular pure hydrogen or hydrogen diluted in a neutralgas. The regeneration can be carried out with a hydrogen pressureranging from 0.01 to 10 MPa, preferably from 0.1 to 2 MPa. It ispossible to proceed in the following way. The feeding of the reactorwith reactant(s) is halted. Hydrogen is subsequently injected and ahydrogen pressure is maintained for a time sufficient to regenerate thecatalyst. Before resuming the metathesis reaction, it is preferable todrive off the excess hydrogen by introducing a neutral gas, e.g. argon.The regeneration temperature is advantageously between 50 and 300° C.,preferably between 80 and 200° C.

The process of the invention can be carried out batchwise in a staticreactor. However, it is preferably carried out continuously in a dynamicreactor.

The term “tungsten hydride grafted to a support based on aluminum oxide”is understood to mean, generally, a tungsten atom bonded to at least onehydrogen atom and, in particular by at least one single bond, to saidsupport.

The metal compound essentially comprises a tungsten hydride grafted to asupport based on aluminum oxide. In this compound, the support can beany support based on aluminum oxide and more particularly any supportwhere the aluminum oxide is accessible in particular at the surface ofsaid support. Thus, the support can be chosen from supports relativelyhomogeneous in composition based on aluminum oxide, having in particulara composition based on aluminum oxide relatively homogeneous throughoutthe body of the support, that is to say from the core up to the surfaceof the support, and also from heterogeneous supports based on aluminumoxide comprising aluminum oxide essentially at the surface of thesupports. In the case of a heterogeneous support, the support cancomprise aluminum oxide deposited on, supported on or grafted to amineral solid which can itself be a solid inorganic support, inparticular chosen from metals, oxides or sulfides, and salts, forexample from silica and metal oxides.

The support can have a specific surface (B.E.T.) chosen within a rangeextending from 0.1 to 1000 m²/g, preferably from 0.5 to 800 m²/g. Thespecific surface (B.E.T.) is measured according to the standard ISO 9277(1995).

The support can in particular comprise aluminum oxide, mixed aluminumoxides or modified aluminum oxides, in particular modified by one ormore elements from Groups 15 to 17 of the Periodic Table of the Elements(as defined by the IUPAC in 1991 in which the groups are numbered from 1to 18 and which is found, for example, in “CRC Handbook of Chemistry andPhysics”, 76th edition (1995-1996), by David R. Lide, published by CRCPress Inc., USA).

The term “aluminum oxide” (also known as simple alumina) is understoodto mean, generally, an aluminum oxide substantially devoid of any otheroxide (or comprising less than 2% by weight of one or more other oxidespresent in the form of impurities). If it comprises more than 2% byweight of one or more other oxides, then it is generally convenient toregard the oxide as a mixed aluminum oxide, that is to say an aluminumoxide combined with at least one other oxide.

The support can preferably comprise aluminum oxide chosen from porousaluminas, nonporous aluminas and mesoporous aluminas.

Porous aluminas are often referred to as “activated aluminas” or“transition aluminas”. They generally correspond to various partiallyhydroxylated aluminum oxides Al₂O₃. They are porous supports generallyobtained by an “activation” treatment comprising in particular a heat(or dehydration) treatment of a precursor chosen from aluminumhydroxides, such as aluminum trihydroxides, hydroxides of aluminum oxideor gelatinous aluminum hydroxides. The activation treatment makes itpossible to remove the water present in the precursor but also, in part,the hydroxyl groups, thus leaving behind a few residual hydroxyl groupsand a specific porous structure. The surface of the porous aluminasgenerally comprises a complex mixture of aluminum and oxygen atoms andof hydroxide ions which combine according to specific crystalline formsand which in particular produce both acidic and basic sites. It is thuspossible to choose, as solid support, a porous alumina from γ-alumina(gamma-alumina), η-alumina (eta-alumina), δ-alumina (delta-alumina),θ-alumina (theta-alumina), κ-alumina (kappa-alumina), ρ-alumina(rho-alumina) and χ-alumina (chi-alumina) and preferably from γ-aluminaand η-alumina. These various crystalline forms depend essentially on thechoice of the precursor and of the conditions of the activationtreatment, in particular the temperature and the pressure. Theactivation treatment can be carried out, for example, under a stream ofair or a stream of another gas, in particular inert gas, at atemperature which can be chosen within a range extending from 100 to1000° C., preferably from 200 to 1000° C.

Use can also be made of porous aluminas or semiporous aluminas preparedby an activation treatment as described above, in particular at atemperature ranging from 600 to 1000° C. These porous or semiporousaluminas can comprise mixtures of porous aluminas in at least one of thecrystalline forms described above, such as γ-alumina, η-alumina,δ-alumina, θ-alumina, κ-alumina, ρ-alumina or χ-alumina, with anonporous alumina, in particular α-alumina, in particular in aproportion of 20 to 80% by weight.

Porous aluminas are generally thermal decomposition products of aluminumtrihydroxides, hydroxides of aluminum oxide (or hydrates of aluminumoxide) and gelatinous aluminum hydroxides (or alumina gels).

Aluminum trihydroxides of general formula Al(OH)₃═Al₂O₃.3H₂O can existin different crystalline forms, such as gibbsite or hydrargillite(α-Al(OH)₃), bayerite (β-Al(OH)₃) or nordstrandite. Aluminumtrihydroxides can be obtained by precipitation from aluminum salts ingenerally alkaline solutions.

Hydroxides of aluminum oxide of general formula AlO(OH)═Al₂O₃.H₂O canalso exist in different crystalline forms, such as diaspore (β-AlO(OH))or boehmite (or α-AlO(OH)). Diaspore can occur in certain types of clayand of bauxite and can be synthesized by heat treatment of gibbsite atapproximately 150° C. or by hydrothermal treatment of boehmite at 380°C. under a pressure of 50 MPa. Boehmite can be easily obtained byheating the gelatinous precipitate formed on treating solutions ofaluminum salts under cold conditions with ammonia. Hydroxides ofaluminum oxide can also be obtained by hydrolysis of aluminum alkoxides.

Gelatinous aluminum hydroxides (or alumina gels) are generallypoly(aluminum hydroxide)s, in particular of general formula:nAl(OH)₃·(n−1)H₂O  (1)in which n is a number varying from 1 to 8. Geiatinous aluminumhydroxides can be obtained by one of the processes chosen from thethermal decomposition of an aluminum salt, such as aluminum chloride,the electrolysis of aluminum salts, such as a mixture of aluminumsulfate and of alkali metal sulfate, the hydrolysis of aluminumalkoxides, such as aluminum methoxide, precipitation from aluminates,such as alkali metal or alkaline earth metal aluminates, andprecipitation from aluminum salts, for example by bringing into contactaqueous solutions of Al₂(SO₄)₃ and of ammonia, or of NaAlO₂ and of anacid, or of NaAlO₂ and of Al₂(SO₄)₃, it being possible for theprecipitates thus obtained to be subsequently subjected to aging anddrying in order to remove the water. Gelatinous aluminum hydroxidesgenerally exist in the form of an amorphous alumina gel, in particularin the form of a pseudoboehmite.

The porous aluminas can have a specific surface (B.E.T.) chosen within arange extending from 100 to 1000 m²/g, preferably from 300 to 1000 m²/g,in particular from 300 to 800 m²/g, especially from 300 to 600 m²/g.They can in addition exhibit a specific pore volume equal to or lessthan 1 cm³/g, preferably equal to or less than 0.9 cm³/g, in particularequal to or less than 0.6 cm³/g.

The support can also comprise nonporous aluminas, preferably α-alumina(alpha-alumina), generally known under the term of “calcined alumina”.α-Alumina exists in the natural state under the term of “corundum”. Itcan be synthesized generally by heat treatment or calcination of aprecursor chosen in particular from aluminum salts, hydroxides ofaluminum oxide, aluminum trihydroxides and aluminum oxides, such asγ-alumina, at a temperature of greater than 1000° C., preferably ofgreater than 1100° C. It can comprise impurities, such as other oxides,for example Fe₂O₃, SiO₂, TiO₂, CaO, Na₂O, K₂O, MgO, SrO, BaO and Li₂O,in proportions of less than 2%, preferably less than 1%, by weight. Thenonporous aluminas, such as α-alumina, can have a specific surface(B.E.T.) chosen within a range extending from 0.1 to less than 300 m²/g,preferably from 0.5 to 300 m²/g, in particular from 0.5 to 250 m²/g.

The support can also comprise mesoporous aluminas having in particular aspecific surface (B.E.T.) chosen within a range extending from 100 to800 m²/g. The mesoporous aluminas generally have pores with a widthranging from 2 nm to 0.05 μm.

The support can also comprise mixed aluminum oxides. The term “mixedaluminum oxides” is understood to mean, generally, aluminum oxidescombined with at least one other oxide in a proportion by weightpreferably from 2 to less than 80%, in particular from 2 to less than50%, especially from 2 to less than 40% or even from 2 to less than 30%.The other oxide or oxides can be oxides of the elements M chosen fromthe metals from Groups 1 to 13 and elements from Group 14, with theexception of carbon, of the Periodic Table of the Elements. Moreparticularly, they can be oxides of the elements M chosen from alkalimetals, alkaline earth metals, transition metals and elements fromGroups 13 and 14 of said table, with the exception of carbon. Thetransition metals generally comprise the metals from Groups 3 to 11 ofsaid table, in particular elements 21 to 29, 39 to 47 and 57 to 79(including lanthanides) and the actinides. The other oxide or oxides ofthe elements M are preferably chosen from the transition metals fromGroups 3 to 7, the lanthanides, the actinides and the elements fromGroups 13 and 14 of said table, with the exception of carbon. Moreparticularly, they can be chosen from silicon, boron, gallium,germanium, titanium, zirconium, cerium, vanadium, niobium, tantalum,chromium, molybdenum and tungsten oxides.

The mixed aluminum oxides can be chosen from anhydrous aluminates, fromspinels and from aluminosilicates. In particular, the anhydrousaluminates can be chosen from anhydrous alkali metal aluminates, such asanhydrous lithium aluminate (LiAlO₂) or anhydrous sodium aluminate(Na₂O.Al₂O₃), and anhydrous alkaline earth metal aluminates, such asanhydrous tricalcium aluminate (3CaO.Al₂O₃) or anhydrous berylliumaluminate (BeO.Al₂O₃). The spinels can be chosen in particular fromaluminum oxides combined with oxides of divalent metals and inparticular from magnesium spinel (MgAl₂O₄), calcium spinel (CaAl₂O₄),zinc spinel (ZnAl₂O₄), manganese spinel (MnAl₂O₄), iron spinel (FeAl₂O₄)and cobalt spinel (CoAl₂O₄). The alumino-silicates can be chosen inparticular from clays, talc, micas, feldspar, microporousaluminosilicates, in particular molecular sieves, and zeolites.

The support can also comprise modified aluminum oxides, in particularmodified by one or more elements from Groups 15 to 17, preferably Groups16 to 17, of the Periodic Table of the Elements, for example phosphorus,sulfur, fluorine or chlorine. The support can in particular comprisealumina superacids or aluminum oxides which are sulfated, sulfided,chlorinated or fluorinated.

The support can be a support homogeneous in composition, in particularthroughout the body of the support. It can also be a heterogeneoussupport based on aluminum oxide, in which support the aluminum oxide,the mixed aluminum oxides or the modified aluminum oxides, as describedabove, are essentially positioned at the surface of the support and thecore of the support is essentially composed of a mineral solid chosen inparticular from metals, oxides or sulfides, and salts, such as silica ormetal oxides. The heterogeneous support can be prepared by dispersingover, by precipitating on and/or by grafting to the mineral solid one ofthe precursors of the compounds based on aluminum oxide mentioned above.The precursors can in particular be chosen from aluminum hydroxides, inparticular from aluminum trihydroxides, hydroxides of aluminum oxide andgelatinous aluminum hydroxides. Preference is given to gelatinousaluminum hydroxides, such as described above, known under the term ofalumina gels or of amorphous aluminas. A heterogeneous support can beprepared in particular by employing such a precursor by way of a sol-gelor using an organo-metallic compound, which facilitates in particularthe grafting to the mineral solid.

The compound according to the invention is generally provided in theform of particles which can have any shape and any size, in particular amean size ranging from 10 nm to 5 mm, preferably from 20 nm to 4 mm. Theparticles of the support can be provided as is or can be shaped so as tohave a specific shape, in particular a spherical, spheroidal,hemispherical, hemispheroidal, cylindrical or cubic shape or the shapeof rings, pellets, disks or granules.

The compound according to the invention essentially comprises a tungstenhydride grafted to the support based on aluminum oxide. The degree ofoxidation of the tungsten in the supported metal compound can have avalue chosen within a range extending from 2 to 6, preferably from 4 to6. The tungsten atom is bonded in particular to the solid support, inparticular via at least one single bond. It can in addition be bonded toone or more hydrogen atoms via single bonds (W—H) and optionally to oneor more hydrocarbon radicals R, in particular via carbon-tungsten singleor multiple bonds. The number of hydrogen atoms bonded to a tungstenatom depends on the degree of oxidation of the tungsten, on the numberof single bonds bonding said tungsten atom to the support and optionallyon the number of single or multiple bonds bonding said tungsten atom tothe hydrocarbon radical R. Thus, the number of hydrogen atoms bonded toa tungsten atom can be at least equal to 1 and at most equal to 5 andcan preferably range from 1 to 4, preferably from 1 to 3. The term“grafting of the tungsten hydride to the solid support based on aluminumoxide” is understood to mean, generally, that the tungsten atom isbonded via at least one single bond to said support and moreparticularly via at least one single bond (W—OAl) to at least one oxygenatom of the aluminum oxide. The number of single bonds bonding thetungsten atom to the support, in particular via a single bond (W—OAl),depends on the degree of oxidation of the tungsten and on the number ofthe other bonds bonding the tungsten atom and is generally equal to 1, 2or 3.

The tungsten atom of the compound according to the invention canoptionally be bonded to one or more hydrocarbon radicals R via one ormore carbon-tungsten single, double or triple bonds. The hydrocarbonradical or radicals R can be identical or different, saturated orunsaturated, hydrocarbon radicals comprising in particular from 1 to 20,preferably from 1 to 10, carbon atoms and optionally comprising silicon,in particular in an organosilane group. They can be chosen in particularfrom alicyclic or aliphatic, in particular linear or branched, alkylradicals, for example alkyl, alkylidene or alkylidyne radicals, inparticular from C₁ to C₁₀ radicals, from aryl radicals, in particularfrom C₆ to C₁₂ radicals, and from aralkyl, aralkylidene or aralkylidyneradicals, in particular from C₇ to C₁₄ radicals.

The tungsten atom of the grafted tungsten hydride can be bonded to thehydrocarbon radical R via one or more carbon-tungsten single, double ortriple bonds. A carbon-tungsten single bond, in particular of σ type,may be concerned: in this case, the hydrocarbon radical R can be analkyl radical, in particular a linear or branched alkyl radical, or anaryl radical, for example, the phenyl radical, or an aralkyl radical,for example the benzyl radical or the radical of formula C₆H₅—CH₂—CH₂—.The term “alkyl radical” is understood to mean, generally, a monovalentaliphatic radical originating from the removal of a hydrogen atom on acarbon atom of the molecule of an alkane or of an alkene or of an alkyneor even of an organosilane, for example a methyl (CH₃—), ethyl (C₂H₅—),propyl (C₂H₅—CH₂—), neopentyl ((CH₃)₃C—CH₂—), allyl (CH₂═CH—CH₂—),alkynyl (R—C≡C—), in particular ethynyl (CH≡C—), or neosilyl((CH₃)₃Si—CH₂—) radical. The alkyl radical can, for example, be offormula R′—CH₂— where R′ represents a linear or branched alkyl radical.

A carbon-tungsten double bond, in particular of π type, may also beconcerned: in this case, the hydrocarbon radical R can be an alkylideneradical, in particular a linear or branched alkylidene radical, or anaralkylidene radical. The term “alkylidene radical” is understood tomean, generally, a divalent aliphatic radical originating from theremoval of two hydrogen atoms on the same carbon atom of the molecule ofan alkane or of an alkene or of an alkyne or even of an organosilane,for example a methylidene (CH₂═), ethylidene (CH₃—CH═), propylidene(C₂H₅—CH═), neopentylidene ((CH₃)₃C—CH═) or allylidene (CH₂═CH—CH═)radical. The alkylidene radical can, for example, be of formula R′—CH═where R′ represents a linear or branched alkyl radical. The term“aralkylidene radical” is understood to mean, generally, a divalentaliphatic radical originating from the removal of two hydrogen atoms onthe same carbon of an alkyl, alkenyl or alkynyl radical connected to anaromatic group.

A carbon-tungsten triple bond may also be concerned: in this case, thehydrocarbon radical R can be an alkylidyne radical, in particular alinear or branched alkylidyne radical, or an aralkylidyne radical. Theterm “alkylidyne radical” is understood to mean, generally, a trivalentaliphatic radical originating from the removal of three hydrogen atomson the same carbon atom of the molecule of an alkane or of an alkene orof an alkyne or even of an organosilane, for example an ethylidyne(CH₃—C≡), propylidyne (C₂H₅—C≡), neopentylidyne ((CH₃)₃C—C≡) orallylidyne (CH₂═CH—C≡) radical. The alkylidyne radical can, for example,be of formula R′—C≡ where R′ represents a linear or branched alkylradical. The term “aralkylidyne radical” is understood to mean,generally, a trivalent aliphatic radical originating from the removal ofthree hydrogen atoms on the same carbon of an alkyl, alkenyl or alkynylradical connected to an aromatic group.

More particularly, the hydrocarbon radical R can be chosen from themethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, neopentyl, allyl,neopentylidene, allylidene, neopentylidyne and neosilyl radicals.

The tungsten atom of the compound according to the invention can becomplexed by one or more hydrocarbon ligands, in particular aromatic orcarbonyl ligands.

The tungsten hydride grafted to the support based on aluminum oxide canbe represented diagrammatically by the following formula:

in which W, Al, O and H respectively represent tungsten, aluminum,oxygen and hydrogen atoms, M represents an atom of one or more elementsof another oxide, such as defined above, R represents a hydrocarbonradical, such as defined above, and x, y, w and z are integers, the sum(w+x+y+z) of which is equal to 2 to 6, and with x=1 to 3, y=1 to 5, w=0to 4 and z=0 to 2. In the formula (2), the —(Al—O) and —(M—O) bondsrepresent one or more single or multiple bonds respectively connectingthe aluminum atom and the atom M to one of the atomic constituents ofthe support based on aluminum oxide, in particular to one of the oxygenatoms of this support.

The compound according to the invention generally exhibits, by infraredspectroscopy, one or more specific absorption bands of the W—H bond, thefrequency of which bands can vary according to the coordination sphereof the tungsten and can depend in particular on the number of bonds ofthe tungsten with the support, with the hydrocarbon radicals R and withother hydrogen atoms. Thus, for example, at least two absorption bandsat 1903 and 1804 cm⁻¹ have been found, which bands are specific inparticular of the W—H bond considered in particular in the environmentof the W—OAl bonds bonding the same tungsten atom to an oxygen atomitself bonded to an aluminum atom of α-alumina. By way of comparison,tungsten hydride grafted under the same conditions to a silica supportgenerally exhibits, by infrared spectroscopy, at least one of the twoabsorption bands at 1940 and 1960 cm⁻¹, which bands are different fromthe above and which are in particular specific of the W—H bondconsidered in particular in the environment of the W—OSi bonds bondingthe same tungsten atom to an oxygen atom itself bonded to a silicon atomof the silica support.

Another way of being able to characterize the presence of a W—H bond inthe compound according to the invention comes from a measurement byproton Nuclear Magnetic Resonance (solid ¹H NMR) at 500 MHz, where thevalue of the chemical shift of the tungsten hydride (δ_(W—H)) is equalto 10.6 ppm (parts per million).

The compound according to the invention can additionally comprise analuminum hydride, in particular at the surface of the support and inparticular in the vicinity of the grafted tungsten hydride. It isbelieved that an aluminum hydride can be formed by opening of analuminoxane bridge (of formula Al—O—Al) present in particular at thesurface of the support and by reaction between a hydrogen atom of agrafted tungsten hydride and the aluminoxane bridge thus opened. Asimple test for the characterization of the aluminum hydride present inthe compound of the invention next to a tungsten hydride comprises areaction for the deuteration of said compound. The test can be carriedout by bringing the compound according to the invention into contactwith a deuterium atmosphere under an absolute pressure of 66.7 kPa, at atemperature chosen between 25 and 80° C., preferably equal to 60° C.,for a period of time of 15 minutes. A selective deuteration reaction isthus carried out under these conditions: it makes it possible tosubstitute the hydrogen atoms by deuterium atoms in the W—H bonds and tothus form new W-D bonds which, by infrared spectroscopy, exhibit twoabsorption bands at 1293 and 1393 cm⁻¹, while leaving unchanged thehydrogen atoms in the Al—H bonds which can then be characterized, byinfrared spectroscopy, by an absorption band at 1914 cm⁻¹.

The present invention also relates to a process for the preparation ofthe supported metal compound. The compound according to the invention,which exists essentially in the form of a tungsten hydride grafted to asupport based on aluminum oxide, can be prepared by a process comprisingthe following stages:

(1) a stage in which an organometallic tungsten precursor (Pr) isdispersed over and grafted to a support based on aluminum oxide, inwhich precursor the tungsten is in particular bonded or complexed to atleast one hydrocarbon ligand, so as to form a tungsten hydrocarboncompound or complex grafted to said support, then

(2) a stage of hydrogenolysis of the grafted tungsten hydrocarboncompound or complex resulting from the preceding stage, so as to form atungsten hydride grafted to said support.

The organometallic tungsten precursor Pr preferably comprises a tungstenatom bonded or complexed to one or more hydrocarbon ligands. Thetungsten atom can in particular be bonded to a carbon of the hydrocarbonligand via carbon-tungsten single, double or triple bonds. Thehydrocarbon ligands can be identical or different, saturated orunsaturated, hydrocarbon radicals, in particular aliphatic or alicyclichydrocarbon radicals, preferably C₁ to C₂₀ radicals, in particular C₁ toC₁₀ radicals, and can be chosen in particular from the hydrocarbonradicals R described above. The number of hydrocarbon ligands bonded tothe tungsten atom depends on the degree of oxidation of the tungsten inthe precursor Pr and can be at most equal to the degree of oxidation ofthe tungsten in the precursor Pr, in particular be greater than 0 and atmost equal to the maximum degree of oxidation of the tungsten andpreferably have any value ranging from 2 to 6, in particular from 4 to6.

The precursor Pr can comprise a tungsten atom in particular complexed toone or more hydrocarbon ligands such that the degree of oxidation of thetungsten is equal to 0. The hydrocarbon ligand can be chosen fromaromatic ligands or carbonyl ligands. Thus, the precursor Pr can bechosen from tungsten bisarene and tungsten hexacarbonyl.

Prior to the first dispersing and grafting stage, the support based onaluminum oxide can be subjected to a preliminary stage of calcinationand/or of dehydroxylation. The support can be calcined so as to oxidizethe carbon possibly present in the support and to remove it in the formof carbon dioxide. The calcination can be carried out by subjecting thesupport to an oxidizing heat treatment, in particular under a stream ofdry air, at a temperature lower than the sintering temperature of thesupport, for example at a temperature ranging from 100 to 1000° C.,preferably from 200 to 800° C., for a sufficient period of time whichmakes it possible to remove the carbon dioxide and which can range from0.1 to 48 hours, under a pressure of less than, equal to or greater thanatmospheric pressure.

The support can also be subjected to another preliminary stage, referredto as dehydroxylation. This stage can be carried out so as to optionallyremove the residual water from the support and a portion of the hydroxylgroups, to leave behind, in particular at the surface of the support, aresidual amount of the hydroxyl groups and to optionally formaluminoxane bridges (of formula Al—O—Al). The dehydroxylation can becarried out by subjecting the support to a heat treatment under an inertgas stream, for example under a stream of nitrogen, of argon or ofhelium, under a pressure preferably of less than atmospheric pressure,for example under an absolute pressure ranging from 10⁻⁴ Pa to 10² kPa,preferably from 10⁻² Pa to 50 kPa, at a temperature of less than thesintering temperature of the support, for example at a temperatureranging from 100 to 1000° C., preferably from 200 to 800° C., and for asufficient period of time which makes it possible to leave anappropriate residual amount of hydroxyl and/or aluminoxane groups in thesupport and which can range from 0.1 to 48 hours. The dehydroxylationstage can advantageously be carried out after the calcination stage.

The dispersing and grafting stage can be carried out by sublimation, byimpregnation using a solvent or by dry mixing. In the case of a stage bysublimation, the precursor Pr, which generally exists in the solid stateunder standard conditions, is heated, in particular under a pressure ofless than atmospheric pressure and under temperature conditions whichprovide for its sublimation and its migration in the gaseous state overthe support. The sublimation can be carried out at a temperature rangingfrom −30 to 200° C. and in particular under an absolute pressure rangingfrom 10⁻⁴ to 1 Pa. The grafting of the precursor Pr to the support canbe monitored by infrared spectroscopy. The excess precursor Pr which hasnot grafted to the support can be removed by reverse sublimation.

The dispersing and grafting stage can also be carried out byimpregnation using a solvent. In this case, the precursor Pr can bedissolved in a polar or nonpolar organic solvent, for example pentane orethyl ether. The impregnation can be carried out by bringing the supportbased on aluminum oxide into contact with the solution, preparedbeforehand, of the precursor Pr. The impregnation can be carried out ata temperature ranging from −80 to 200° C., under an inert atmosphere,for example an atmosphere of nitrogen, of argon or of helium, andpreferably with stirring. A suspension of a tungsten hydrocarboncompound or complex grafted to the support is thus obtained. The excessprecursor Pr which has not grafted to the support can be removed bywashing using an organic solvent identical to or different from thatused during the impregnation.

The dispersing and grafting stage can also be carried out by dry mixing,in particular by dry mechanical mixing, in the absence of liquid or ofliquid solvent. In this case, the precursor Pr, which is present in theform of a solid, is mixed with the support based on aluminum oxide inthe absence of liquid or of liquid solvent, in particular withmechanical stirring and under an inert atmosphere, for example anatmosphere of nitrogen, of argon or of helium, so as to form a mixtureof two solids. During or after the dry mixing, it is possible to carryout a heat treatment and/or a treatment under a pressure of less thanatmospheric pressure, so as to bring about the migration and thereaction of the precursor Pr with the support. The precursor which hasnot been grafted to the support can be removed by reverse sublimation orby washing using an organic solvent.

The preparation of the compound according to the invention can comprisea second stage referred to as hydrogenolysis. It is a reaction for thehydrogenolysis of the tungsten hydrocarbon compound or complex graftedto the support as prepared in the preceding stage. The reaction isgenerally carried out so as to form a tungsten hydride grafted to thesupport. The term “hydrogenolysis” is understood to mean, generally, areaction in which a molecule is cleaved with attachment of hydrogen tothe two cleaved portions. To be specific, the cleavage reaction takesplace in particular between the tungsten atom grafted to the support andthe carbon atom of the precursor Pr attached to or complexed with saidtungsten atom. The hydrogenolysis can be carried out using hydrogen or areducing agent capable in particular of converting the grafted tungstenhydrocarbon compound or complex to grafted tungsten hydride. Thehydrogenolysis can be carried out by bringing the grafted tungstenhydrocarbon compound or complex into contact with hydrogen or thereducing agent. It can be carried out under a hydrogen atmosphere or aninert atmosphere, when a reducing agent is used, under an absolutepressure ranging from 10⁻² to 10 MPa, at a temperature ranging from 20to 500° C., for a period of time ranging from 0.1 to 48 hours.

The present invention furthermore relates to the use of the supportedmetal compound according to the invention and as disclosed in FR 0303588 in a process employing cleavage and recombination reactions ofCsp²═Csp² olefinic double bonds to manufacture novel olefins. It relatesmore particularly to the use of the compound according to the inventionas catalyst in reactions for the metathesis of an olefin with itself(self-metathesis) or with at least one other olefin (crossed metathesis)as represented in the above equations (1) and (2).

The following examples illustrate the present invention.

EXAMPLE 1 Preparation of a Tungsten Hydride Grafted to an Alumina

In a preliminary stage, 530 mg of a γ-alumina, having a mean size of 40μm and a specific surface (B.E.T.) of 200 m²/g, comprising 90% by weightof alumina and 9% by weight of water and sold by Johnson Matthey (GreatBritain), are subjected to a calcination treatment under a stream of dryair at 500° C. for 15 hours and then to a dehydroxylation treatmentunder an absolute pressure of 10⁻² Pa at 500° C. for 15 hours, so thatthe alumina thus calcined and dehydroxylated exhibits, by infraredspectroscopy, three absorption bands respectively at 3774, 3727 and 3683cm⁻¹ characteristic in particular of residual AlO—H bond.

In a first stage, the 530 mg of the alumina prepared above areintroduced into a glass reactor under an argon atmosphere and at 25° C.,followed by a solution of 6 ml of n-pentane comprising 300 mg oftris(neopentyl)neopentylidynetungsten, used as precursor Pr andcorresponding to the general formula:W[—CH₂—C(CH₃)₃]₃[≡C—C(CH₃)₃]  (3)

The mixture thus obtained is maintained at 25° C. for 3 hours. At theend of this time, a tungsten organometallic compound grafted to thealumina is obtained, the excess precursor Pr which has not reacted beingremoved by washing with n-pentane at 25° C. The tungsten organometalliccompound thus grafted is dried under vacuum. It comprises 1.5% by weightof tungsten and corresponds to the general formula:(Al—O)_(x)W[—CH₂—C(CH₃)₃]_(y)[═CH—C(CH₃)₃]  (4)with x=1 and y=2.

In a second stage, 50 mg of the grafted tungsten organometallic compoundobtained above are isolated and subjected in a glass reactor to ahydrogenolysis treatment by bringing into contact with hydrogen under anabsolute hydrogen pressure of 73 kPa at 150° C. for 15 hours. At the endof this time, the reactor is cooled to 25° C. and a compound (W/Al-1)according to the invention, which comprises in particular a tungstenhydride grafted to the alumina, is obtained and isolated under argon.The compound (W/Al-1) comprises 1.5% by weight of tungsten and exhibits,by infrared spectroscopy, two absorption bands respectively at 1903 and1804 cm⁻¹ characteristic of the W—H bond grafted in particular to thealumina.

EXAMPLE 2 Preparation of a Tungsten Hydride Grafted to an Alumina

The preliminary stages of calcination and of dehydroxylation of theα-alumina are absolutely identical to those of example 1.

In a first stage, 53 mg of the alumina prepared above are isolated andintroduced into a glass reactor at 25° C. under an argon atmosphere. Theprecursor Pr of general formula (3) as used in example 1 is thenintroduced into the reactor. The reactor is then heated at 70° C. for 2hours, so as to sublime the precursor Pr over the alumina and to form atungsten organometallic compound grafted to the alumina. At the end ofthis time, the excess precursor Pr which has not reacted is removed byreverse sublimation at 70° C. Subsequently, the reactor is cooled to 25°C. and a tungsten organo-metallic compound thus grafted which comprises3.7% by weight of tungsten and which corresponds to the precedinggeneral formula (4) is isolated under argon.

The second stage is carried out exactly as in example 1, except for thefact that use is made of the tungsten organometallic compound grafted tothe alumina prepared in the preceding stage. A compound (W/Al-2)according to the invention comprising a tungsten hydride grafted to thealumina and comprising 3.7% by weight of tungsten is thus obtained. Itexhibits, by infrared spectroscopy, two absorption bands respectively at1903 and 1804 cm⁻¹ characteristic of the W—H bond grafted in particularto the alumina.

The compound (W/Al-2) is subjected to a selective deuteration test whichshows that it comprises a tungsten hydride and an aluminum hydride, bothgrafted to the alumina. A sample of the compound (W/Al-2) is placed in aglass reactor and is then brought into contact, in this reactor, with adeuterium atmosphere under an absolute pressure of 66.7 kPa at atemperature of 60° C. for 15 minutes. At the end of this time, thereactor is cooled to 25° C. and the solid compound thus deuterated isisolated under argon; this compound exhibits, by infrared spectroscopy,an absorption band at 1914 cm⁻¹ characteristic of the Al—H bondunchanged by the deuteration reaction carried out under theseconditions. Furthermore, it is observed that the absorption bands at1903 and 1804 cm⁻¹ characteristic of the W—H bond grafted to the aluminadisappear to the advantage of the absorption bands respectively at 1293and 1393 cm⁻¹ characteristic of the W-D bond grafted to the alumina andformed by the deuteration reaction of the W—H bonds.

EXAMPLE 3 Preparation of a Tungsten Hydride Grafted to an Alumina

The preliminary stages of calcination and of dehydroxylation of thealumina are absolutely identical to those described in example 1.

In a first stage, 2 g of the alumina prepared above are isolated andintroduced under an argon atmosphere into a glass reactor at 25° C.equipped with a magnetic stirring bar. 305 mg of the precursor Pr ofgeneral formula (3) as used in example 1 are then introduced into thereactor. The reactor is heated to 66° C. and the dry mixture thusprepared is stirred for 4 hours. At the end of this time, the reactor iscooled to 25° C. and then the solid mixture is washed with n-pentane at25° C. The solid compound thus washed is dried under vacuum and thenisolated under argon, so as to obtain a tungsten organometallic compoundgrafted to the alumina comprising 3.9% by weight of tungsten andcorresponding to the preceding general formula (4).

The second stage is carried out exactly as in example 1, except for thefact that use is made of the tungsten organometallic compound grafted tothe alumina prepared above. A compound (W/Al-3) according to theinvention comprising a tungsten hydride grafted to the alumina andcomprising 3.9% by weight of tungsten is thus obtained. It exhibits, byinfrared spectroscopy, two absorption bands respectively at 1903 and1804 cm⁻¹ characteristic of the W—H bond grafted to the alumina.Furthermore, it exhibits, by nuclear magnetic resonance (solid ¹H NMR)at 500 MHz, a value of the chemical shift of the tungsten hydride(δ_(W—H)) equal to 10.6 ppm (parts per million).

EXAMPLE 4 Preparation of a Tungsten Hydride Grafted to a Silica/Alumina

In a preliminary stage, 530 mg of a silica/alumina, having a specificsurface (B.E.T.) of 475 m²/g, comprising 33% by weight of alumina andsold by Akzo Nobel, are subjected to a calcination treatment under astream of dry air at 500° C. for 15 hours and then to a dehydroxylationtreatment under an absolute pressure of 10⁻² Pa at 500° C. for 15 hours,so that the silica/alumina thus calcined and dehydroxylated exhibits, byinfrared spectroscopy, an absorption band at 3747 cm⁻¹ characteristic inparticular of residual SiO—H bond.

In a first stage, the 530 mg of silica/alumina prepared above areintroduced into a glass reactor under an argon atmosphere and at 25° C.,followed by a solution of 6 ml of n-pentane comprising 300 mg of theprecursor Pr of general formula (3) as used in example 1.

The mixture thus obtained is maintained at 25° C. for 3 hours. At theend of this time, a tungsten organo-metallic compound grafted to thesilica/alumina is obtained, the excess precursor Pr which has notreacted being removed by washing with n-pentane at 25° C. The tungstenorganometallic compound thus grafted is dried under vacuum. It comprises1.5% by weight of tungsten and corresponds to the general formula:(Si—O)_(x)W[—CH₂—C(CH₃)₃]_(y)[═CH—C(CH₃)₃]  (5)with x=1 and y=2.

In a second stage, 50 mg of the grafted tungsten organometallic compoundobtained above are isolated and are subjected, in a glass reactor, to ahydrogenolysis treatment by bringing into contact with hydrogen under anabsolute hydrogen pressure of 73 kPa at 150° C. for 15 hours. At the endof this time, the reactor is cooled to 25° C. and a compound (W/SiAl-1)according to the invention which comprises in particular a tungstenhydride grafted to silica/alumina is obtained and isolated under argon.The compound (W/SiAl-1) comprises 1.5% by weight of tungsten andexhibits, by infrared spectroscopy, two absorption bands respectively at1906 and 1804 cm⁻¹ characteristic of the W—H bond grafted in particularto silica/alumina.

EXAMPLE 5 Preparation of a Tungsten Hydride Grafted to a Silica/Alumina

The preliminary stages of calcination and of dehydroxylation of thesilica/alumina are absolutely identical to those described in example 3.

In a first stage, 1 g of the silica/alumina prepared above is isolatedand introduced under an argon atmosphere into a glass reactor at 25° C.equipped with a magnetic stirring bar. 305 mg of the precursor Pr ofgeneral formula (3) as used in example 1 are then introduced into thereactor. The reactor is heated at 66° C. and the dry mixture thusproduced is stirred for 4 hours. At the end of this time, the reactor iscooled to 25° C. and then the solid mixture is washed with n-pentane at25° C. The solid compound thus washed is dried under vacuum and thenisolated under argon, so as to obtain a tungsten organometallic compoundgrafted to the silica/alumina comprising 7.5% by weight of tungsten andcorresponding to the preceding general formula (5).

The second stage is carried out exactly as in example 1, except for thefact that use is made of the tungsten organometallic compound grafted tothe silica/alumina prepared above. A compound (W/SiAl-2) according tothe invention comprising a tungsten hydride grafted to thesilica/alumina and comprising 7.5% by weight of tungsten is thusobtained. It exhibits, by infrared spectroscopy, two absorption bandsrespectively at 1903 and 1804 cm⁻¹ characteristic of the W—H bondgrafted to the silica/alumina. Furthermore, it exhibits, by nuclearmagnetic resonance (solid ¹H NMR) at 500 MHz, a value of the chemicalshift of the tungsten hydride (δ_(W—H)) equal to 10.6 ppm (parts permillion).

EXAMPLE 6 Reaction for the Metathesis of Propene Catalyzed by W/Al-3 ina Static Reactor

The supported metal compound (W/Al-3) prepared according to example 3 isused in a reaction for the metathesis of propene which can berepresented by the following equation:

The experiment is carried out in the following way: the supported metalcompound is prepared “in situ” in a glass reactor as described inexample 3. The reactor is subsequently placed under vacuum, then filledwith propene up to a pressure of 76 kPa and, finally, heated at 150° C.The formation is then observed of a mixture essentially of ethylene, ofn- and isobutenes, and also of pentenes and hexenes in smaller amounts,which are analyzed and quantitatively determined by gas chromatography(capillary column KCl/Al₂O₃, 50 m×0.32 mm; detection by flameionization).

The cumulative conversion of propene, which is the number of moles ofpropene converted with respect to the number of moles of propeneintroduced initially, and the number of rotations (T.O.N.) or cumulativenumber of moles of propene converted over time per mol of tungsten ofthe supported metal compound are calculated.

The selectivities (SC₂), (SC₄), (SC₅) and (SC6) for the various productsare also calculated respectively according to the following equations:

-   SC₂=(number of moles of ethylene formed)/(total number of moles of    olefins formed)-   SC₄=(number of moles of n-butenes formed)/(total number of moles of    olefins formed)-   SC₅=(number of moles of pentenes formed)/(total number of moles of    olefins formed)-   SC6=(number of moles of hexenes formed)/(total number of moles of    olefins formed)

The results of the measurements and calculations defined above for thereaction for the metathesis of propene as a function of the time arecollated in table 1 below.

Selectivities of the products formed (%) Cumulative SC₂ SC₄ SC₅ SC₆ Timeconversion ethylene butenes pentenes hexenes (h) (%) T.O.N. (%) (%) (%)(%) 0 0 0 0 0 0 0 0.33 32.8 481 50.6 47.3 1.87 0.23 0.75 38.43 565 51.8845.6 2.21 0.28 1.33 41.26 600.6 49.46 47.37 2.92 0.43 2 41.8 605.6 48.547.76 3.24 0.62 3 42.5 611 46.75 49.33 3.3 0.62

Metathesis of propene in a static reactor catalyzed by WH/α-alumina(W/Al-3) at 150° C.; M cat=50 mg (% W=3.86%), V reactor=505 ml, Ppropene=76 kPa Propene/Ws=1470

EXAMPLE 7 Reaction for the Metathesis of Propene Catalyzed by W/Al-3 ina Static Reactor

The experiment is carried out in a similar way to example 6, except thatthe reaction is carried out at 80° C.

The results of the measurements and calculations as defined in example 6for the reaction for the metathesis of propene as a function of the timeare collated in table 2 below.

Selectivities of the products formed (%) Cumulative SC₂ SC₄ SC₅ SC₆ Timeconversion ethylene butenes pentenes hexenes (h) (%) T.O.N. (%) (%) (%)(%) 0.25 14.96 219 53.09 46.91 0 0 0.5 20.07 294 51.61 48.39 0 0 1 23.56346 53.39 46.61 0 0 2 27.53 404 52.65 47.35

EXAMPLE 8 Reaction for the Metathesis of Propene Catalyzed by W/Al-3 ina Dynamic Reactor

The complex (Al—O)_(x)W[—CH₂—C(CH₃)₃]_(y)[═CH—C(CH₃)₃] (4) grafted tothe alumina by sublimation (200 mg; 3.86% W/Al₂O₃; 42 micromol of W)according to example 3 is transferred in a glove box into a tubularstainless steel reactor which can be isolated from the atmosphere. Afterconnecting the reactor to the assembly, the circuit is purged with argonand then the supported tungsten hydride catalyst [W]_(s)—H is preparedin situ by treatment of the grafted alkyl-alkylidyne complexes under astream of hydrogen (3 ml/min) at 150° C. for 15 h, resulting in thecompound (W/Al-3). After cooling to 25° C., the reactor is purged of theexcess hydrogen with argon and then under a stream of propene at 101.3kPa (5 ml/min, i.e. a molar flow rate of 5.31 propene/W/min). Thereactor is then rapidly brought to the temperature of 150° C. (rise of250° C./h). The products are analyzed on line by gas chromatography(capillary column KCl/Al₂O₃, 50 m×0.32 mm; detection by flameionization). The formation is then observed mainly of ethylene, ofbutenes, of pentenes and of hexenes in small amounts.

The results of the measurements and calculations as defined in example 6for the reaction for the metathesis of propene as a function of the timeare collated in table 3 below. In this case, an instantaneousconversion, which is the number of moles of propene converted withrespect to the number of moles of propene introduced at each instant, isdefined.

Instan- Molar composition of the gas phase in % taneous SC₂ SC₃ SC₄ SC₅SC₆ SC₇ conver- Cumula- ethyl- pro- bu- pen- hex- hep- Time sion tiveene pylene tenes tenes enes tenes (h) (%) T.O.N. (%) (%) (%) (%) (%) (%)0 0 0 0 0 0 0 0 0 14 40 1784 18.5 60 19.6 1.44 0.4 0.07 31 39.3 395018.6 60.7 19 1.25 0.33 0.06 48 38.7 6117 18.6 61.3 18.7 1.15 0.28 0.0565 38.4 8283 18.5 61.6 18.4 1.07 0.26 0.046 114 37.5 14 528 18.31 62.518 0.93 0.21 0.037 148 37.7 18 861 18.1 62.3 18.5 0.87 0.2 0.033 18236.44 23 194 18 63.56 17.4 0.82 0.18 0.031 203 36.24 25 870 17.95 63.7617.28 0.79 0.17 0.029 213 36.1 27 144 17.87 63.9 17.2 0.78 0.17 0.029

EXAMPLE 9 Ethylene/2-Butene Crossed Metathesis Reaction Catalyzed byW/Al-3 in a Static Reactor

The experiment is carried out in a similar way to example 6, except thatthe reaction is carried out at 150° C. with a 50/50 molar mixture ofethylene and of 2-butene instead of propene. Propene is then mainlyformed according to the reaction:

The results of the measurements and calculations as defined in example 6for the ethylene/2-butene crossed metathesis reaction as a function ofthe time are collated in table 4 below.

Molar composition of the gas phase (%) Time C₂ (%) C₄ (%) C₃ (%) C₅ (%)C₆ (%) (h) ethylene butenes propene pentenes hexenes 0 55 45 0 0 0 0.2539.28 30 30 0.64 0.04 0.75 28.58 24.68 45.93 0.7 0.1 1.25 24.1 21.852.07 1.13 0.15 2 21.78 20.71 56.05 1.27 0.17

EXAMPLE 10 Regeneration under Hydrogen of the Catalyst W/Al-3 in aDynamic Reactor

After having operated as in example 8, the catalyst (W/Al-3) isregenerated in a dynamic reactor under a stream of hydrogen (4 ml/min,0.1 MPa) at 150° C. for 15 h. The catalyst, thus regenerated, thenregains its activity in the metathesis of propene.

It should be clearly understood that the invention defined by theappended claims is not limited to the specific embodiments indicated inthe above description but encompasses the alternative forms thereofwhich depart neither from the scope nor from the spirit of the presentinvention.

1. A process for the metathesis of one or more reactants comprising alinear or branched hydrocarbon chain comprising an olefinic double bondCsp²═Csp², in which this reactant or these reactants is/are reacted inthe presence of a supported metal compound comprising a support based onaluminum oxide to which a tungsten hydride is grafted.
 2. The process asclaimed in claim 1, in which the reactant or reactants each comprise(s)from 2 to 30 carbon atoms.
 3. The process as claimed in claim 1, inwhich the reactant is an unsaturated, linear or branched, acyclichydrocarbon, comprising a Csp²═Csp² double bond between two carbonatoms, of empirical formula C_(n)H_(2n), n being an integer ranging from2 to
 30. 4. The process as claimed in claim 1, in which ethylene andbutene are reacted to produce propylene.
 5. The process as claimed inclaim 1, in which the compound corresponds to the formula R₁R₂C═CR₃R₄ inwhich identical or different R_(i) (i=1 to 4) substituents are chosenfrom hydrogen atoms, saturated, linear or branched, hydrocarbon groupsand saturated cyclic hydrocarbon groups which optionally carryhydrocarbon substituents and which can be connected to the Csp² carbonof the olefinic double bond either directly or via a saturatedhydrocarbon chain.
 6. The process as claimed in claim 1, in which thecompound corresponds to the formula R₁R₂C═CR₃R₄ in which identical ordifferent R_(i) (i=1 to 4) substituents are chosen from hydrogen atoms,saturated, linear or branched, hydrocarbon groups and aromatic ringswhich optionally carry saturated hydrocarbon substituents and which canbe connected to the Csp² carbon of the olefinic double bond eitherdirectly or via a saturated hydrocarbon chain.
 7. The process as claimedin claim 1, in which the degree of oxidation of the tungsten has a valuechosen within a range extending from 2 to
 6. 8. The process as claimedin claim 1, in which the tungsten atom is bonded to one or more hydrogenatoms and optionally to one or more hydrocarbon radicals R.
 9. Theprocess as claimed in claim 8, in which the hydrocarbon radicals R areidentical or different, saturated or unsaturated, hydrocarbon radicalscomprising from 1 to 20 carbon atoms and optionally comprising silicon.10. The process as claimed in claim 1, in which the tungsten hydride isgrafted to the support based on aluminum oxide according to thefollowing scheme:

in which W, Al, O and H respectively represent tungsten, aluminum,oxygen and hydrogen atoms, M represents an atom of one or more elementsof another oxide, R represents a hydrocarbon radical and x, y, w and zare integers, the sum (w+x+y+z) of which is equal to 2 to 6, and withx=1 to 3, y=1 to 5, w=0 to 4 and z=0 to 2, the —(Al—O) and —(M—O) bondsrepresenting one or more single or multiple bonds respectivelyconnecting the aluminum atom and the atom M to one of the atomicconstituents of the support based on aluminum oxide, in particular toone of the oxygen atoms of this support.
 11. The process as claimedclaim 1, in which the support is chosen from supports homogeneous incomposition based on aluminum oxide and from heterogeneous supportsbased on aluminum oxide comprising aluminum oxide essentially at thesurface of said heterogeneous supports.
 12. The process as claimed inclaim 1, in which the support comprises aluminum oxide, mixed aluminumoxides or modified aluminum oxides.
 13. The process as claimed in claim1, in which the reaction is carried out at a temperature ranging from 20to 600° C.
 14. The process as claimed in claim 1, in which the reactionis carried out under an absolute pressure ranging from 0.01 to 8 MPa.15. The process as claimed in claim 1, in which the metal compound isregenerated in the presence of hydrogen.
 16. The process as claimed inclaim 15, in which the regeneration is carried out at a temperature ofbetween 50 and 300° C.
 17. The process as claimed in claim 15, in whichthe regeneration is carried out with a hydrogen pressure ranging from0.01 to 10 MPa.
 18. The process as claimed in claim 7, wherein the rangeextends from 4 to
 6. 19. The process as claimed in claim 9, wherein thehydrocarbon radicals comprise 1 to 10 carbon atoms.
 20. The process asclaimed in claim 13, wherein the temperature ranges from 20 to 350° C.21. The process as claimed in claim 13, wherein the temperature rangesfrom 50 to 300° C.
 22. The process as claimed in claim 13, wherein thetemperature ranges from 80 to 200° C.
 23. The process as claimed inclaim 14, wherein the absolute pressure ranges from 0.01 MPa to 1 MPa.24. The process as claimed in claim 14, wherein the absolute pressureranges from 0.1 MPa to 0.5 MPa.
 25. The process as claimed in claim 16,wherein the temperature is between 80 and 200° C.
 26. The process asclaimed in claim 17, wherein the hydrogen pressure ranges from 0.1 to 2MPa.